Time interval measuring and recording arrangement



T. R. LONG 3,324,43 TIME INTERVAL MEASURING AND RECORDING IRRANCTEMENT`June 6, 's

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OUTPUT TERM 24 York Filed @et 7, 1963, Ser. No. 314,321 17 Claims. (Cl.340-174) This invention relates to electronic timing circuits and, morespecifically, to an arrangement which accurately measures andautomatically records the time at which events of interest occur.

A plurality of electronic timing circuits are well known in the art anddescribed, for example, in vol. 20 of the Radiation Laboratory Series,entitled, Electronic Time Measurements, edited by B. Chance et al.,copyrighted by McGraw-Hill in 1949. One typical prior art arrangement,employed to compute the time interval between two sequentially occurringevents, comprises -a fixed frequency pulse source which is gated on andoff, respectively, responsive to the occurrence of the first and secondevents. By counting the number of pulses supplied by the pulse source,the time interval may readily be determined. A second relatively commontime measuring embodiment utilizes a single sinusoidal signal and aphase detector. In such an arrangement the timing information is derivedfrom the phase differential undergone Iby the sinusoid between the timeswhen the relevant events transpire.

However, the above and other prior art timing arrangements becomeincreasingly complex and difficult to fabricate as the time intervals tobe measured become relatively small. Moreover, if permanent storage ofthe timing information is desired, ancillary memory elements mustusually be provided. Further, the timing information supplied by priorart embodiments is ordinarily analog in nature, and analog-to-digitalconverters must be employed if binary encoded output signals arerequired.

It is therefore an object of the present invention to provide animproved electronic timing arrangement.

More specifically, an object of the present invention is the provisionof a circuit arrangement which accurately measures and records the timeswhen any desired number of events of interest occur.

Another object of the present invention is a time measuring arrangementwhich automatically records timing information in binary form suitablefor data processing.

Still another object of the present invention is the provision of anelectronic time measuring arrangement capable of measuring very shortperiods of time with high resolution.

Yet another object of the present invention is the provision of a timemeasuring and recording arrangement which is highly reliable, and whichmay be easily and inexpensively constructed.

These and other objects of the present invention are realized in aspecific, illustrative time interval measuring and recording arrangementwhich includes a set of thin film ferromagnetic storage elements. Thefilm elements each have their easy axes of magnetization coupled to aplurality of output terminals included on a harmonic generator whichsupplies thereto a fundamental frequency oscillation and a plurality ofeven harmonics thereof. A

3,324,453 Patented .lune 6, 1967 biasing current source is coupled tothe hard magnetization axes of the thin film elements.

When an event of interest occurs, the biasing source is deenergized.Responsive thereto, the magnetization of each film spot rotates to aselected orientation along the easy film axis, which orientation isdetermined by the instantaneous polarity of the associated harmonicsignal. The storage pattern in the film devices uniquely identifies thetime relative to the start of the fundamental frequency oscillation whenthe event transpired, to an accuracy of one-half the period of thehighest harmonic. If it is desired to time a plurality ofsequentially-occurring events, additional sets of film elements areemployed.

It is thus a feature of the present invention that a time intervalmeasuring arrangement employ a harmonic generator which supplies afundamental frequency oscillation, and a plurality of even harmonicsthereof, to quantize a time interval.

It is another feature of the present invention that a time measuringarrangement include a plurality of thin film magnetic elements havingthe easy axes thereof coupied to sinusoidal magnetizing forcescharacterized by a fundamental frequency and a plurality of evenharmonies thereof, and that the arrangement further include a normallyenergized biasing source coupled to the hard axes of the thin filmelements, and an event detector for de-energizing the bias source.

A complete understanding of the present invention and of the above andother features, advantages and variations thereof, may be gained from aconsideration of the following detailed description yof an illustrativeembodiment thereof presented hereinbelow in conjunction with theaccompanying drawing, in which:

FIG. 1 is a diagram of an illustrative time measuring and recordingarrangement which embodies the principles of the present invention;

FIG. 2 is a timing diagram illustrating a first set of currentsassociated with selected circuit elements illustrated in FIG. 1; and

FIG. 3 is a timing diagram illustrating an alternative set of currentsassociated with selected circuit elements `illustrated in, FIG. l.

Referring now to FIG. l, there is shown a specific illus'- trative timeinterval measuring and recording arrangement which includes a first setof ferromagnetic thin film elements 10 through 13 and a second set offilm elements 50 through 53. A plurality of signal windings 41 through44- are respectively coupled to the easy magnetization axes of the firstset of film elements 10 through 13 and also to the easy axes of thesecond set of elements 50 through 53. The windings 41 through 44 haveone end portion thereof grounded with the other winding end portionsbeing ,respectively connected to a plurality of output terminals 21through 24 which are included on a harmonic generator 20. The generator2.0 supplies a fundamental frequency sinusoidal current signal to theoutput terminal 21, and further supplies currents characterized by thesecond, fourth, and eighth harmonic frequencies of the fundamentalsinusoid to the remaining output terminals 22 through 24 in that order.The currents supplied to the terminals 21 through 24 are respectivelyillustrated in the upper four curves included in FIG. 2.

By respectively assigning the binary designations 0 and "1 to thepositive vand negative polarity of each sinusoid supplied by thegenerator 20, it is noted that the time interval corresponding to eachhalf cycle of the eighth harmonic current shown in the fourt-h curve inFIG. 2 is identified by a unique binary word, as illustrated in Table Ifollowing:

TABLE I Polarity Polarity Polarity Polarity Half Cycle of the ofthe ofthe of the of the Eight Harmonie Funda- Second Fourth Eigth Currentmental Harmonic Harmonie Harmonic Sinusoid Thirteenth 1 1 0 0Fourteenth- 1 1 0 1 Fifteenth 1 1 1 0 Sixteenth 1 1 1 1 It is noted thatthe above encodmg comprises a stra1ght binary counting code, with themost significant digit being in the left-hand column. Hence, forexample, the binary word 1001, which has `a decimal equivalent of 9,identifies the time interval coincident with the tenth half cycle of theeighth harmonic signal (since the first half cycle is represented by adecimal 0).

Two bias current sources 60 and 65 are included in the FIG. 1arrangement. The source 60 is coupled by a first bias winding 64 to thehard axis of each of the first set of thin film elements through 13.Similarly, the bias source 65 is coupled to the hard magnetization axisof each of the thin film elements 50 through 53 by a second bias winding69. The bias sources 6i) and 65 each include an ON input terminal 61 and66, respectively, and also an OFF input terminal 62 and 67,respectively.

The sources 60 and 65 respectively supply `direct currents in thedirection of the vectors 100 and 110 shown in FIG. 1 to the associatedbias windings 64 and 69 when the ON terminals 61 and 66 thereof havebeen last activated. When the OFF terminals 62 and 67 thereof have beenlast supplied with an input signal, the sources 60 an-d 65 do not supplycurrents to the associated biasing windings 64 `and 69.

First and second event detectors 80 and 81 are respectively connected tothe OFF input terminals 62 and 67 included on the biasing sources 60 and65. The event detectors 80 and 81 are employed Ito supply a voltageincrement to the OFF terminal of the associated source upon theoccurrence of an event to which they are responsive. In addition, a readout source 70 has two output terminals 71 and 72 thereon lrespectivelyconnected to the ON terminals 61 and 66 included on the biasing sources60 and 65. The source 70 sequentially supplies voltage signals to theoutput terminals 71 and 72 included thereon in that order. Finally, anoutput register 90 has four input terminals 91 through 94 thereonrespectively connected to the signal windings 41 through 44 via'one of aplurality of filter means 8S through 88. Each of the filters 85 through88 is adapted to present an extremely high impedance at the sinusoidalfrequency associated with the signal winding connected thereto whilepresenting a low impedance to output pulse information.

With the above organization in mind, an illustrative sequence of circuitoperation for the FIG. 1 time measuring and recording arrangement willnow be described. The initial condition for the magnetization vectorssymbolizing the instantaneous magnetic states of the thin film elements10 through 13 and 50 through 53 is in a vertically up orientation alongthe hard magnetization axes. This initial condition is achieved by aninitial condition source 83 included in the FIG. 1 arrangement directingthe read out source 70 to supply pulses to the output terminals 71 and72 thereon. These pulses supplied by the source 70 activate the biassources 60 and 65, thereby energizing the associated biasing windings 64and 69 with direct currents in the direction indicated by the vectors100 and 110. The requisite initial current conditions for the windings64 and 69 are respectively shown in the lower two curves included inFIG. 2 for the interval preceding time a shown therein.

Assume now that an event occurs at time a to which the first eventdetector 80 is responsive. This event may advantageously comprise astart signal to establish a time reference or, alternatively, an actualevent of interest. The detector senses the event at time a and suppliesa voltage pulse to the OFF input terminal 62 included on the biasingsource 60. Responsive to this received input pulse, the source 60de-energizes the biasing winding 64 connected thereto, as shown in thenext-tothe-bottom curve included in FIG. 2 for the interval followingtime a. When the biasing magnetizing force is rcmoved from the hard axisdirection of each of the first set of thin film elements 10 thr-ough 13by the de-energization of the biasing winding 64, the magnetizationvector in each of the film elements 10 through 13 rotates from itsformer orientation along the hard axis to now reside along the easy axisof magnetization of the corresponding film element. The particulardirections along the easy axis to which the magnetization vectorsrespectively rotate are dependent upon the instantaneous polarities ofthe magnetizing forces supplied along the easy axis, which are, in turn,solely a function of the instantaneous polarities of the sinusoidalcurrents supplied to the associated signal windings 41 through 44. Withthe specific winding pollarities employed in the FIG. 1 timingarrangement, a positive sinusoidal signal current flowing downwardsthrough a signal winding will cause the associated magnetization vectorto rotate to a left- -to-right orientation along the easy axis, while anupwardtiowing, negative sinusoidal current will give rise to aright-to-left easy axis orientation. This tipping, or rotating mode ofoperation is unique to thin film elements, and has been discussed atgreat length in the literature. See, for example, Theoretical HysteresisLoops of Thin Magnetic Films, by H. J. Oguey in the June 1960 issue ofthe Proceedings of the I.R.E.

At the time a shown in FIG. 2, it may be observed that the fundamentalfrequency oscillation and the second and eighth harmonic sinusoidalsignal currents, respectively supplied to the windings 41, 42 and 44,have a positive value whereas the fourth harmonic signal supplied to thewinding 43 has a negative value. Hence, when the hard axis bias isremoved from the thin film elements 10 through 13 at time a, themagnetization vectors in the film elements 10, 11 and 13 will rotate toa left-to-right orientation along the easy axis of these elements, whilethe vector in the film element 12 will reside in a right-toleft easyaxis polarity. Thus, as will become more apparent from the followingdiscussion, digital-type information which specifically identifies thetime interval corresponding to the particular eighth harmonic half cyclewhich includes the time a is stored in the film elements 10 through 13,which information is represented by the selective pattern of easy axismagnetic conditions for these film devices.

Assume now that a second event of interest occurs at the time b shown inthe lower curve included in FIG. 2. Responsive thereto the second eventdetector 81 supplies a signal to the OFF input terminal 67 included onthe source 65. Upon receiving a signal from the detector 81 at time b,the source 65 becomes deactivated and no current is supplied to theassociated biasing winding 69, as shown in the lower graph of FIG. 2. Asmay be observed in the upper four graphs included in FIG. 2, thefundamental frequency oscillation and the fourth harmonic sinusoid havenegative values at' time b, while the second and eighth harmonic signalshave positive values. Hence, when the magnetization vectors included inthe film elements 50 through 53 rotate toward the easy magnetizationaxis responsive to the de-energization of the biasing winding 69, thefilm devices 50 and 52 reside in a right-to-left orientation along theeasy axis, and the lm elements 5 and 53 reside in a left-to-rightpolarity.

When the timing information stored in the film devices through 13 and S0through 53 is desired, the read out source 70 first supplies a signal tothe output terminal 71 at time c, and later supplies an output signal tothe terminal 72 at time d. The times c and d are respectively shown inthe bottom two curves included in FIG. 2. When the biasing source 60receives the signal supplied thereto lby the source 70 at the time c,the source 60 once again supplies a biasing current to the associatedbiasing winding 64, as shown in the next-to-the-bottom curve included inFIG. 2. Responsive to the applied magnetizing force supplied thereto bythe energized biasing winding 64, the magnetization vectors included inthe first set of film spots 10 through 13 each rotate upwards to avertical, hard direction magnetization axis. The upward rotation of themagnetization in the films 10, 11 and 13, which started from aleft-to-right easy axis orientation, induces negative voltage pulses inthe associated signal windings 41, 42 and 44. These negative signals aretransmitted via the filter means 85, S5 and 88 to output terminals 91,92 and 94 included on the output register 90. As noted hereinabove, thefilter means 85 through 88 inhibit the associated sinusoidal currentsfrom passing therethrough to the output register 90, while allowing thepassage of the output pulse information.

On the other hand, as the magnetic. rotation of the lm element 12started from a right-to-left easy axis polarity prior to the time c, apositive signal is induced in the associated signal winding 43 by themagnetic vector rotation occurring the element 12. This positive outputpulse is coupled from the winding 43 to the output register terminal 93via the filter means 87. Hence, adopting the binary terminology that apositive output signal is a binary l and a negative signal is a binary0, the binary word 0010 is supplied to the output register terminals 91through 94 at time c. It is noted that this binary word has the decimalequivalent 2, hence specifying that the event transpiring at time aoccurred during the time interval corresponding to the third half cycleof the highest, or eighth harmonic sinusoid, as indicated by Table Isupra.

Responsive to the read-out pulse supplied by the source 70 at time d,the bias current source 65 at this time energizes the bias winding 69,as shown in the bottom curve of FIG. 2. The winding 69 therebyconstrains the magnetization vectors in the second set of film spots 50through 53 to rotate to their upward, hard direction axes. Responsivethereto, positive pulses are supplied to the output terminals 91 and 93since the film spots 50 and 52 resided in a right-to-left easy axisorientation prior to the time d.

In a similar manner, negative pulses are supplied to the outputterminals 92 and 94. Employing the convention adapted hereinabove, thebinary word 1010 is supplied to the register terminals 91 through 94.This word has a decimal equivalent of 10 which, as may be observed fromTable I supra, indicates that the time b occurred during the timeinterval coincident with the eleventh half cycle of the eighth harmonicsignal.

Following the time d, the FIG. 1 arrangement is reset to the requisiteinitial condition described above, and is ready to measure and recordthe times at which two new events of interest are detected by the eventdetectors 80 and 811. Thus, the FIG. 1 arrangement has been shown tomeasure and record the times, relative to the beginning of a cycle ofthe fundamental frequency oscillation, at which two events haveoccurred.

It should ibe observed that the FIG, 1 time measuring arrangement has amaximum time error corresponding to the duration of one half cycle ofthe highest harmonic frequency employed. Hence, the FIG. 1 arrangementmay be designed to measure time to any desired accuracy by simplyemploying a suitable number of harmonics. In general, if time is to bemeasured to an accuracy of within A time units, the highest harmonicfrequency must be at least 1/2A. Hence, since thin films are operable toat least 1000 megacycles, the FIG. 1 arrangement may advantageously bedesigned to measure time to within 0.5 nanosecond.

Several things are noted at this point. First, the arnplitude of thesinusoidal currents supplied by the harmonic generator 20 mayadvantageously be designed to be capable of effectively saturating thefilm elements 10 through 13 and 50 through 53 along their easy axes foralmost the entirety of each half cycle of oscillation when the hard axisbias is removed. This would constrain the output signals supplied to theregister 90 to be of a uniform arnplitude. Alternatively, a like resultwould obtain if conventional limiters were interposed between thefilters through 88 and the corresponding register terminals 91 through94.

Also, it is observed that a number of sinusoidal signal currentcombinations exist, in addition to the pattern shown in the upper fourcurves illustrated in FIG. 2, which may advantageously be supplied bythe harmonic generator 20 to the output termin-als 21 through 24 touniquely quantize a time interval into sixteen equal portions (or anyother desired number depending on the timing accuracy required). Onesuch combination is illustrated in FIG. 3 wherein the output terminals21 through 24 are respectively supplied with a fundamental frequencysignal and a fundamental frequency, second harmonic and fourth harmonicsignal each advanced by ninety degrees. By employing the binaryconvention adopted hereinabove regarding the FIG. 2 sinusoids, viz., abinary 0 and a binary 1 respectively correspond to a positive andnegative sinusoidal polarity, the Graycoded binary time intervalrepresentation shown in Table Il infra results for each of the sixteenquarter cycles of the fourth harmonic current:

TABLE II Polarity Polarity Polarity Polarity Quarter Cycle of the of theofthe of the of the Fourth Funda- Second Fourth Eighth Harmonie Currentmental Harmonie Harmonic Harmonie Sinusoid O 0 0 0 0 0 0 1 0 0 1 1 0 0 10 0 1 1 0 0 1 1 1 0 1 0 1 0 1 0 0 1 1 0 0 1 1 0V 1 1 1 1 1 Twelfth 1 1 10 Thirteenth 1 0 1 0 Fourteenth 1 0 1 1 Fifteenth. 1 '0 0 1 Sixteenth 10 0 0 The Gray code illustrated in Table II has the desirable property.that only one of the four binary digits changes betweenany twocontiguous -time intervals. Hence, if an error occurs in any digit whenan event is recorded, the error would correspond in time to the durationof only a single quarter cycle of the fourth harmonic signal. Also notelthat only one of the four sinusoids illustrated .in FIG. 3 passesthrough zero at any single time. Hence, if `an event occurs at or nearany of these times, any error which results would be included in only asingle digit which, as discussed above, amounts to a time error of onlya quarter period of the fourth harmonic signal.

summarizing, an illustrative time measuring and recording arrangementmade in accordance with the principles of the present inventioncomprises .a set of thin film magnetic storage elements. The Ifilmelements each have their easy axes of magnetization coupled to aplurality of output terminals included in a harmonic generator whichsupplies thereto a fundamental frequency oscillation and a plurality ofeven harmonics thereof. A biasing current source is coupled to the hardmagnetization axes of the film elements.

When an event of interest occurs, the biasing source is de-energized.Responsive thereto, the magnetization vector in each film spot rotatesto a selected orientation along the easy film axis, which orientation isdetermined by the instantaneous polarity of the associated harmonicsignal. The storage pattern in the film devices uniquely identities thetime, relative to the start of the fundamental frequency oscillation,when the event transpired, to an accuracy of one-half the period of thehighest harmonic. If it -is desired to time a plurality ofsequentially-occurring events, .additional sets of film elements areemployed.

I-t is to be understood that the above-described arrangements are onlyillustrative of the application of the principles of the presentinvention. Numerous other arrangements may be devised by those skilledin the art without departing from the spirit and scope of thisinvention. For example, while the FIG. l time measuring and recordingarrangement was illustrated as being capable of processing twosequentially-occurring events, there is no limit to the capacity of suchan arrangement. For each additional event to be monitored, an additionalset of thin films along with an additional bias current source and eventdetector would simply be employed.

Also, note that the sole requirements on the signals supplied by thegenerator are that they be bipolar and of the specified frequencyrelationship. Thus, bipolar square wave pulses supplied, for example, bya plurality of selected stages of a binary counter may advantageously beemployed in the FIG. 1 arrangement.

Further, note that gating means may be employed in place of the filters8S through 88 to pass only output information from the film elements tothe register 90. The gating means would connect the signal windings 41through 44 to the harmonic source output terminals 21 through 24 and theregister input terminals 91 through 94, respectively, during the timemeasuring and read out portions of circuit operation.

What is claimed is:

1. yIn combination, a harmonic generating source for supplying outputsignals comprising a fundamental frequency bipolar oscillation and aplurality of harmonics thereof, a first plurality of magnetic thin lmstorage elements each including an easy and a hard axis ofmagnetization, and la plurality of windings each coupled to `a differentthin film element along its easy axis of magnetization and connected tosaid harmonic source, said source supplying each of said windings with adifferent one of said oscillations.

2. A combination `as in claim 1 further comprising first biasing meanscoupled to each of said plurality of thin lm elements along its hardmagnetization axis.

3. A combination as in claim 2 further comprising an event detectorconnected to said biasing means for selectively de-energizing saidbiasing means.

4. A combination as in claim 3 further comprising an output registerconnected to each of said plurality of windings.

5. A combination yas in claim 4 further comprising filter means seriallyinterposed between said output register and said plurality of windings.

6. A combination as in claim 1 wherein said harmonic generating sourcecomprises oscillating means for supplying a fundamental frequency signaland a plurality of even harmonics thereof, the frequencies of saidharmonics following a geometric progression.

7. A combination as in claim 3 further comprising a second plurality ofmagnetic thin tilm storage elements each element including an easy and ahard axis of magnetization, each element included in said second filmplurality being coupled along its easy magnetization axis to a differentone of said plurality of windings, and second biasing means coupled toeach of -said second plurality of thin film magnetic elements along itshard axis of magnetization.

8. In combination, a harmonic generating source for supplying outputsignals comprising a fundamental frelquency bipolar oscillation and aplurality of even harmonies thereof, an enabling means, a plurality ofbistable storage elements each connected to said enabling means and tosaid harmonic generator, lsaid harmonic generating source supplying eachof said plurality of bistable elements with a different frequencyoscillation, each of said bistable elements being responsive to anenabling signal supplied by said enabling means for residing in a firststable state when said associated harmonic signal is of a first polarityand for residing in a second stable state when said associated harmonicsignal is of a second polarity.

9. A combination as in claim 8 wherein said enabling means includes anevent detector.

10. A combination as in claim 9 further comprising read-out meansconnected to each of said bistable means for switching each of saidbistable means to a like condition.

11. A combination as in claim 10 wherein each of said bistable meansincludes a magnetic thin film element each including a hard axis ofmagnetization and wherein said enabling means further includes a biasingcurrent source connected to said event detector and coupled to each ofsaid thin film elements along its hard axis of magnetization.

12. In combination, a harmonic generating source for supplying aplurality of differing oscillating signals, a first plurality ofmagnetic thin film storage elements each including an easy and a hardaxis of magnetization, a plurality of windings each coupled to adifferent thin film element along its easy axis of magnetization andconnected to said harmonic source, said source supplying each of saidwindings with a different one of said oscillations.

13. A combination as in claim 12 further comprising biasing meanscoupled to each of said first plurality of thin film elements along itshard magnetization axis.

14. A combination as in claim 13 further comprising an event detectorconnected to said biasing means for selectively de-energizing saidbiasing means.

15. A combination as in claim 14 further comprising an output register,and means connecting said output register to each of said plurality ofwindings.

16. A combination as in claim 12 wherein said harmonic generating sourcecomprises means for supplying a plurality of binary Gray-coded bipolarsignals.

17. In combination, a harmonic generating source for supplying outputsignals comprising a fundamental frequency bipolar oscillation and aplurality of even harmonics thereof, a plurality of magnetic thin filmstorage elements each including an easy and a hard axis ofmagnetization, and a plurality of windings each coupled to a differentthin film element along its easy axis of magnetization and connected tosaid harmonic source, said source supplying each of said first windingswith a different one of said oscillations.

No references cited.

BERNARD KONICK, Primary Examiner.

J. W. MOFFI'IT, Assistant Examiner.

17. IN COMBINATION, A HARMONIC GENERATING SOURCE FOR SUPPLYING OUTPUTSIGNALS COMPRISING A FUNDAMENTAL FREQUENCY BIPOLAR OSCILLATION AND APLURALITY OF EVEN HARMONICS THEREOF, A PLURALITY OF MAGNETIC THIN FILMSTORAGE ELEMENTS EACH INCLUDING AN EASY AND A HARD AXIS OFMAGNETIZATION, AND A PLURALITY OF WINDINGS EACH COUPLED TO A DIFFERENTTHIN FILM ELEMENT ALONG ITS EASY AXIS OF MAGNETIZATION AND CONNECTED TOSAID HARMONIC SOURCE, SAID SOURCE SUPPLYING EACH OF SAID FIRST WINDINGSWITH A DIFFERENT ONE OF SAID OSCILLATIONS.